The present invention relates to the field of immunology and is particularly concerned with antigenically-marked non-infectious retrovirus-like particles (sometimes termed pseudovirions).
Human immunodeficiency virus is a human retrovirus and is the etiological agent of acquired immunodeficiency syndrome (AIDS). Since AIDS was first reported in the US in 1981, more than 194,000 people have died of AIDS and over 330,000 cases of HIV infection have been reported in the US alone. Worldwide it is estimated that more than 14 million people have been infected with HIV.
More than 100 AIDS-related medicines are in human clinical trials or awaiting FDA approval but there is currently no cure for the disease.
There is therefore a clear need for immunogenic preparations useful as vaccine candidates, as antigens in diagnostic assays and kits and for the generation of immunological reagents for diagnosis of HIV and other retroviral disease and infection.
Particular prior art immunogenic preparations include non-infectious, non-replicating HIV-like particles. Thus PCT applications WO 93/20220 published Oct. 14, 1993 and WO 91/05860 published May 2, 1990 (Whitehead Institute for Biomedical Research), teach constructs comprising HIV genomes having an alteration in a nucleotide sequence which is critical for genomic RNA packaging, and the production of non-infectious immunogenic HIV particles produced by expression of these constructs in mammalian cells.
PCT application WO 91/07425 published May 30, 1991 (Oncogen Limited Partnership) teaches non-replicating retroviral particles produced by coexpression of mature retroviral core and envelope structural proteins such that the expressed retroviral proteins assemble into budding retroviral particles. A particular non-replicating HIV-1 like particle was made by coinfecting mammalian host cells with a recombinant vaccinia virus carrying the HIV-1 gag and protease genes and a recombinant vaccinia virus carrying the HIV-1 env gene.
In published PCT application WO 91/05864 in the name of the assignee hereof, (which is incorporated herein by reference thereto) there is described particular non-infectious non-replicating retrovirus-like particles containing at least gag, pol and env proteins in their natural conformation and encoded by a modified retroviral genome deficient in long terminal repeats and containing gag, pol and env genes in their natural genomic arrangement.
Since there is no vaccine nor effective treatment for AIDS and since such prior art HIV-like particles contain many of the HIV proteins in their natural conformations, a host immunized therewith may mount an immune response immunologically indistinguishable from infection by HIV. Heat-inactivated anti-HIV antiserum obtained from HIV-infected people and inactivated HIV are currently commercially available as components of many diagnostic methods. For safety, ease of handling, shipping, storage and use it may be preferable to replace such heat-inactivated antisera and antigens by non-infectious HIV and antisera generated by immunization with non-infectious HIV particles as described above. Furthermore, antisera generated by immunization with these non-infectious HIV particles do not require heat inactivation to remove infectious HIV. However, because of the seriousness of HIV infection it is desirable to be able to distinguish between inactivated HIV and non-infectious, non-replicating HIV particles and antisera generated by virulent HIV and non-infectious, non-replicating HIV particles. Thus, in the development of AIDS vaccine candidates, immunogenic preparations and diagnostic methods and kits, it would be useful to provide an HIV-like particle immunologically or otherwise distinguishable from virulent HIV.
The present invention is concerned with the ability to differentiate between infection by HIV or another retrovirus, particularly a human retrovirus, and immunization with an immunogenic preparation. The present invention is also concerned with the ability to differentiate between inactivated virulent HIV and non-infectious non-replicating HIV-like particles. The present invention incorporates a marker into a non-infectious, retrovirus-like particle.
Accordingly, in one aspect, the present invention provides a non-infectious retrovirus-like particle, comprising an assembly of (a) an env gene product; (b) a pol gene product; (c) a gag gene product; and (d) at least one antigenic marker which is non-retroviral or non-HIV retroviral.
The at least one antigenic marker may have about 5 to about 100 amino acid residues, particularly about 10 to about 75 amino acid residues. The antigenic marker may comprise at least one antigenic epitope from another virus. The invention is illustrated, in one embodiment, by at least one antigenic epitope from tobacco mosaic virus (TMV) coat protein, specifically including an amino acid sequence AFDTRNRIIEVEN (SEQ ID NO: 1) or a portion, variation or mutant thereof capable of eliciting antibodies that recognize this sequence, or multiple copies, specifically from 1 to 4, of such amino acid sequence.
The antigenic marker may be incorporated into the assembly of env, pol and gag gene products in any convenient manner. In one embodiment of the invention, the marker sequence is contained within the gag gene product to form a hybrid gag gene product having the particle-forming characteristics of unmodified gag gene product. The marker sequence may be contained within the gag gene product by insertion of the antigenic marker into the gag gene product at an antigenically-active insertion site.
In one specific embodiment of the invention, the insertion site may be that located between amino acid residues 210 and 211 of the gag gene product of the HIV-1 LAI isolate or the corresponding location of other retroviral gag gene products.
The marker sequence also may be provided by deleting or preventing production of an amino acid sequence that corresponds to an epitope of a retroviral protein. Such epitope may comprise the immunodominant epitope of gp41, which provides endogenous anchoring function. When such endogenous anchoring function is removed in this way, the anchoring function is provided by a different antigenic anchor sequence.
Accordingly, in another aspect of the present invention, there is provided a non-infectious retrovirus-like particle, comprising an assembly of (a) a modified env gene product in which endogenous anchoring function has been replaced by a different anchor sequence operatively connected to the env gene product to anchor the env gene product to the retrovirus-like particle; (b) a pol gene product; and (c) a gag gene product.
The anchor sequence, which may be antigenic, may have between about 5 and about 100 amino acid residues, preferably about 10 to about 75 amino acid residues. The anchor sequence may comprise at least a portion of a transmembrane component of a membrane-spanning protein, particularly a glycoprotein. Such glycoprotein may be any convenient glycoprotein, such as an influenza virus protein, particularly a human influenza virus protein, or an avian influenza virus protein.
The anchor sequence may include an amino acid sequence WILWISFAISCFLLCVVLLGFIMW (SEQ ID NO: 2) or a portion, variation or mutant thereof capable of producing antibodies that recognize that sequence, an amino acid sequence STVASSLALAIMIAGLSFWMCSNGSLQ (SEQ ID NO: 3) or a portion, variation or mutant thereof capable of producing antibodies that recognize that sequence; or an amino acid sequence WILWISFAISCFLLCVVCWGSSCGPAKKATLGATFAFDSKEEWCREKK EQWE (SEQ ID NO: 4) or a portion, variation or mutant thereof capable of producing antibodies that recognize that sequence.
The anchor sequence preferably is inserted into the env gene product adjacent to and upstream of functional cleavage sites of the env gene product. The insertion site preferably is located between amino acid residues 507 and 508 of the env gene product of the HIV-1 LAI isolate or the corresponding location of other retroviral env gene products.
The retrovirus-like particle preferably is one in which the env, pol and gag gene products correspond to the env, pol and gag gene products of a human retrovirus, particularly HIV-1, HIV-2, HTLV-1 or HTLV-2. Specifically, the human retrovirus may be HIV-1 and the env gene product may be an LAI env gene product, an MN env gene product, an env gene product from a primary HIV-1 isolate, or an env gene product antigenically equivalent thereto.
The present invention also includes nucleic acid molecules encoding non-infectious, retrovirus-like particles of the invention. Accordingly, in another aspect of the invention, there is provided a nucleic acid molecule encoding a non-infectious retrovirus-like particle, comprising a modified retroviral genome deficient in long terminal repeats and containing gag, pol and env genes in their natural genomic arrangement and a segment encoding at least one antigenic marker which is non-retroviral or non-HIV retroviral. The nucleic acid molecule may comprise a DNA molecule containing the characteristic genetic elements present in a SacI to XhoI fragment of the genome of the HIV-1LAI isolate. The modified genome also may be deficient in primer binding site.
In one specific illustrative embodiment of this aspect of the invention, the sequence encoding the at least one antigenic marker is inserted into the gag gene, specifically at the PstI site at nucleotide 1415 of the gag gene of HIV-1 LAI isolate or the corresponding location of other retroviral gag genes. One specific segment comprises from 1 to 4 copies of a DNA sequence selected from the group consisting of:
(a) 5xe2x80x2 GCATTCGACACTAGAAATAGAATAATAGAAGTTGAAAAT 3xe2x80x2; (SEQ ID NO: 5);
(b) 3xe2x80x2 CGTAAGCTGTGATCTTTATCTTATTATCTTCAACTTTTA 5xe2x80x2; (SEQ ID NO: 6); and
(c) DNA sequences that hybridize with (a) or (b) under stringent conditions, particularly sequences that have at least about 90% sequence identity with the sequence of (a) or (b).
A variety of hybridization conditions may be employed to achieve varying degrees of selectivity of hybridization. For a high degree of selectivity, stringent conditions are used to form the duplexes, such as low salt and/or high temperature conditions, such as provided by 0.02 M to 0.15 M NaCl at temperatures of between about 50xc2x0 C. to 70xc2x0 C. For some applications, less stringent hybridization conditions are required such as 0.15 M to 0.9 M salt, at temperatures ranging from between about 20xc2x0 C. to 55xc2x0 C. Hybridization conditions can also be rendered more stringent by the addition of increasing amounts of formamide, to destabilize the hybrid duplex.
In a yet further embodiment of the present invention, there is provided a nucleic acid molecule encoding a non-infectious retrovirus-like particle, comprising a modified retroviral genome deficient in long terminal repeats and containing gag, pol and env genes in their natural genomic arrangement with the env gene being modified to provide therein a segment encoding an antigenic anchor sequence to anchor the env gene product to the retrovirus-like particle, whereby the modified env gene encodes a modified env gene product in which endogenous anchoring function of env has been replaced by the antigenic anchor sequence.
In one specific illustrative embodiment of this aspect of the invention, the segment encoding the antigenic marker sequence is inserted into the env gene, specifically between nucleotides 7777 and 7778 of the env gene of the HIV LAI isolate or the corresponding location of other retroviral env genes. One specific segment encoding the anchor sequence includes a DNA sequence selected from the group consisting of:
(a) 5xe2x80x2 TGGATCCTGTGGATTCCTTTGCCATATCATGCTTTTTGCTTTG TGTTGTTTTGCTGGGGTTCATCATGTGG 3xe2x80x2; (SEQ ID NO: 7);
(b) 3xe2x80x2 ACCTAGGACACCTAAAGGAAACGGTATAGTACGAAAAACGAAAC ACAACAAAACGACCCCAAGTAGTACACC 5xe2x80x2; (SEQ ID NO: 8); and
(c) DNA sequences that hybridize with (a) or (b) under stringent conditions, particularly sequences that have at least about 90% sequence identity with the sequences of (a) or (b).
Another specific segment encoding the anchor sequence includes a DNA sequence selected from the group consisting of:
(a) 5xe2x80x2 TCAACAGTGGCAAGTTCCCTAGCACTGGCAATCATGATAGCTGGTC TATCTTTTTGGATGTGTTCCAATGGGTCATTGCAG 3xe2x80x2 (SEQ ID NO: 9);
(b) 3xe2x80x2 AGTTGTCACCGTTCAAGGGATCGTGACCGTTAGTACTATCGACCA GATAGAAAAACCTACACAAGGTTACCCAGTAACGTC 5xe2x80x2 (SEQ ID NO: 10); and
(c) DNA sequences that hybridize with (a) or (b) under stringent conditions, particularly sequences that have at least about 90% sequence identity with the sequences of (a) or (b). A further specific segment encoding the anchor sequence includes a DNA sequence selected from the group consisting of:
(a) 5xe2x80x2 TGGATCCTGTGGATTTCCTTTGCCATATCATGCTTTT TGCTTTGTGTTGTTTGCTGGGGTTCATCATGTGGGCCTGCCAAAA AGGCAACATTAGGTGCAACATTTGCATTTGATAGTAAAGAAGAGTGGTGC AGAGAGAAAAAAGAGCAGTGGGAA 3xe2x80x2 (SEQ ID NO: 11);
(b) 3xe2x80x2 ACCTAGGACACCTAAAGGAAACGGTATAGTACGAAAAACGAA ACACAACAAACGACCCCAAGTAGTACACCCGGACGGTTTTTCCGTTGTAA TCCACGTTGTAAACGTAAACTATCATTTCTTCTCACCACGTCTCTCTTTT TTCTCGTCACCCTT 5xe2x80x2 (SEQ ID NO: 12); and
(c) DNA sequences that hybridize with (a) or (b) under stringent conditions, particularly sequences that have at least about 90% sequence identity with the sequence of (a) or (b).
The present invention further includes, in an additional aspect, an immunogenic composition capable of eliciting a retroviral specific immune response and a specific immune response against a non-retroviral marker, comprising the retrovirus-like particles or nucleic acid molecule provided herein, and a carrier therefor. Such composition may be formulated for mucosal or parenteral administration, by oral, anal, vaginal or intranasal routes. The immunogenic composition may comprise at least one other immunogenic or immunostimulating material, specifically an adjuvant, such as aluminum phosphate, aluminum hydroxide, Freund""s incomplete adjuvant or QS21.
In a further aspect, the present invention includes a method of immunizing a host to produce a retroviral specific immune response and a specific non-retroviral immune response against an antigenic marker, comprising administering to the host an immunoeffective amount of the immunogenic composition provided herein.
The present invention also includes diagnostic procedures and kits utilizing these materials. Specifically, in another aspect of the invention, there is provided a method of determining the presence of antibodies specifically reacting with retrovirus antigens in a sample, comprising the steps of (a) contacting the sample with the non-infectious retrovirus-like particle provided herein to produce complexes comprising the non-infectious retrovirus-like particles and any such antibodies present in the sample specifically reactive therewith; and (b) determining production of the complexes.
In an additional aspect of the invention, there is provided a method of determining the presence of retroviral antigens in a sample, comprising the steps of (a) immunizing a host with the immunogenic composition provided herein to produce retroviral antigen-specific antibodies; (b) contacting the sample with the retroviral antigen-specific antibodies to produce complexes comprising any retrovirus antigens in the sample and the retroviral antigen-specific antibodies; and (c) determining production of the complexes.
A further aspect of the invention provides a diagnostic kit for detecting the presence of retroviral antigens in a sample comprising (a) at least one such retroviral antigen-specific antibody provided herein; (b) means for contacting the at least one antibody with the sample to produce a complex comprising any retroviral antigens in the sample and the retroviral antigen-specific antibodies; and (c) means for determining production of the complex.
Further, in an additional aspect of the invention, there is provided a method of identifying antiserum generated by immunization with the immunogenic composition provided herein, comprising detecting antibodies in the antiserum specific for the antigenic marker.
Advantages of the present invention include:
an immunogenic retrovirus-like particle comprising gag, pol and env gene products in their natural conformations rendered non-infectious and non-replicating; and
an immunogenic retrovirus-like particle immunologically distinguishable from a virulent retrovirus.